Granular polytetrafluoroethylene powders and process for producing the same

摘要

To provide a filler-containing or non-filler-containing polytetrafluoroethylene granular powder having a high apparent density, a small electrostatic charge and a superior powder flowability and giving a molded product which is free from lowering of tensile strength and elongation and coloring attributable to the surfactant and has a high degree of whiteness, and a process for preparing the same. The granulation is carried out by wetting 100 part by weight of a polytetrafluoroethylene powder or a mixture of polytetrafluoroethylene powder and filler with 30 to 60 parts by weight of an aqueous solution containing a nonionic surfactant having a hydrophobic segment comprising a poly(oxyalkylene) unit having 3 or 4 carbon atoms and a hydrophilic segment comprising a poly(oxyethylene) unit and then applying a mechanical force to the wetted polytetrafluoroethylene powder or the wetted mixture of polytetrafluoroethylene powder and filler.